Feedback on beginner math program

Jul 13, 2013 at 8:50pm
Obsidian (1)
If this is the proper place to ask for feedback on the efficiency of code, then here is a short program I wrote today. I just started C++ today, and have no other
experience with coding.

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#include <iostream>
#include <math.h>
using namespace std;

int main() {
    
    string n,answers;
    double a,b;
    double c,d;
    int i,is_prime;
    
    label1:
    cout << "Input a number.\n";
    cin >> a;
    cout << "The square of " << a << " is " << a*a << ".\n";
    cout << "The cube of " << a << " is " << a*a*a << ".\n";
    
    if ((int)a % 2 == 0)
       cout << a << " is an even number.\n";
    else
        cout << a << " is an odd number.\n";
    
    i = 2;
    while (i <= sqrt(static_cast<double>(a))) {
          if ((int)a % i == 0)
          is_prime = false;
          i++;
          }
    
    if (is_prime)
       cout << a << " is a prime number.\n";
    else
        cout << a << " is not a prime number.\n";
    
    cout << "Would you like to continue? (y/n): ";
    cin >> n;
    if (n == "y")
       goto labelcont;
    if (n == "yes")
       goto labelcont;
    if (n == "n")
       goto labelend;
    if (n== "no")
       goto labelend;    
    else 
         cout << "Improper syntax, closing... \n";
         goto labelend;
         
    labelcont:
    cout << "What would you like to do? (+,-,*,/,restart,end): ";
    cin >> answers;
    
    if (answers == "+")
       goto label_plus;
    if (answers == "-")
       goto label_minus;
    if (answers == "*")
       goto label_mult;
    if (answers == "/")
       goto label_div;
    if (answers == "r")
       goto label1;
    if (answers == "restart")
       goto label1;
    if (answers == "e")
       goto labelend;
    if (answers == "end")
       goto labelend;
    else cout << "Incorrect syntax. Closing...";
    goto labelend;
    
    label_plus:
    cout << "Enter a number to start with: ";
    cin >> a;
    cout << "\nEnter a number to add to " << a << ": ";
    cin >> b;
    cout << "\n" << a << " + " << b << " = " << a+b << "\n\n";
    goto labelcont;
    
    label_minus:
    cout << "Enter the first number: ";
    cin >> a;
    cout << "\nEnter the second number: ";
    cin >> b;
    cout << "\n" << a << " - " << b << " = " << abs((int)a-(int)b) << "\n\n";
    goto labelcont;
    
    label_mult:
    cout << "Enter the first number: ";
    cin >> a;
    cout << "\nEnter the number to multiply by " << a << ": ";
    cin >> b;
    cout << "\n" << a << " * " << b << " = " << a*b << "\n\n";    
    goto labelcont;
    
    label_div:
    cout << "Enter the first number: ";
    cin >> a;
    cout << "\nEnter the second number: ";
    cin >> b;
    cout << "\n" << a << " / " << b << " = " << a/b << "\n\n";
    goto labelcont;
    
    labelend:
    return 0;
}
Edit & run on cpp.sh


I would just like some feedback on the code, preferably methods on how I can optimize it. I have noticed a lot of people hate 'goto', but I could not think of another way to have the program go back to the start without it.
Jul 13, 2013 at 9:05pm
metulburr (585)
all the goto's can be replaced if you restructure your program using functions, and loops.
Jul 13, 2013 at 9:08pm
ar2007 (210)

in your code,can delete the goto statement if you use switch instead of if / else, with the addition of functions.
Last edited on Jul 13, 2013 at 9:09pm
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